CltOCODILIANS, LIZAKDS, AND SNAKES. 707 



peutes, although they form as a whole an ascending line. The line of 

 the Tortricina and Scoleeophidia is such, as already remarked, and 

 these are approached by the ground Peropoda, as Uryx, Charma, etc. 

 Nearly every division of the ascending line exhibits degenerate side 

 branches, and mostly of a similar type. Thus in the Opisthoglypha we 

 have the small burrowing type of TantiUa and similar forms in Amer- 

 ica, and in Africa Aparallactus and others. Of Proteroglypha, EUips 

 shows a tendency in the same direction, and in Yermicella (Australia) 

 it is more pronounced. The same thing is observable in most of the 

 divisions of the Aglyphodonta. The Old World Calamarina^, which 

 approach nearest the Peropoda, present many such types. In the 

 Aglyphodont series the acquisition of the calyculate structure of the 

 hcmipenis with spines is evidence of advanced type, the flounced cliar- 

 acter being inferior and directly affiliated with the Calamarian and 

 Peropodiin. We have in the Colubrinte examples of degenerate types 

 (mostly in Central America), where the calyces become reduced in num- 

 ber and the proportion of spines increased in connection with degen- 

 eracy in other respects. The same degeneracy in primal structure may 

 take place when the flounces become obsolete and spines only are left. 

 It is possible that the Natricine group aci^uired its primal character in 

 this way, without having passed through a calyculate stage. This 

 group also has its specially degenerate forms in America, as Storeria, 

 Virginia., and Haldea. 



Among the Solenoglypha we have a conspicuous examjile of degen- 

 eracy in the African genus Atractaspis, which, like the other examples 

 above cited, is a burrower in its habits. In external appearance it 

 considerably resembles the Opisthoglyph genus Aparallactus , of the 

 same region. Degeneracy of the hemipenis by loss of calyces and 

 extension of spines is seen in the genera Cerastes and UcJiis. 



The degeneracy so far referred to consists in the reduction of the 

 mechanism of rapid movement, the contraction of the mouth parts, the 

 reduction of the eyes, and the shortening of the tail. All of these con- 

 sequences have probably resulted from the adoption of a more or less 

 subterranean life, or "earth-parasitism," as I have termed it, as they 

 certainly are associated in life. Another kind of degeneracy, whicli is 

 less common, is the attenuation of bones surrounding the mouth and 

 the reduction in number and size of the teeth, conditions associated 

 with the use of soft food, as caterpillars, etc This is exhibited by the 

 iamily of the Amblycephalidu', which live in the forests of the Indian 

 and neotropical regions. Accompanying the reduction of the jaws is 

 an abbreviation of the muzzle, which, with the large eye, gives a very 

 fcBtal character to the head. 



Having thus cleared the main lines of degenerate comidications, we 

 could trace the ascending series of the Aglyphodonta, had we the mate- 

 rial. This is unfortunately insufficient. That the Xatricina' are a 

 distinct line is attested by their continue<l vertebral hypapophyses, 



